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Secretion is the movement of material from one point to another, such as a secreted chemical substance from a cell or gland. In contrast, excretion is the removal of certain substances or waste products from a cell or organism. The classical mechanism of cell secretion is via secretory portals at the plasma membrane called porosomes. [1]
DNA cloning can be performed spontaneously by the cell for reproductive purposes. This is a form of asexual reproduction where an organism splits into fragments and then each of these fragments develop into mature, fully grown individuals that are clones of the original organism (See reproductive fragmentation). DNA cloning can also be ...
Holocrine gland secretion is the most damaging (to the cell itself and not to the host which begot the cell) type of secretion, with merocrine secretion being the least damaging and apocrine secretion falling in between. Examples of holocrine glands include the sebaceous glands of the skin [2] [3] and the meibomian glands of the eyelid.
During apoptosis (programmed cell death), the cell's cytoskeleton breaks up and causes the membrane to bulge outward. [13] These bulges may separate from the cell, taking a portion of cytoplasm with them, to become known as apoptotic blebs. [14] Phagocytic cells eventually consume these fragments and the components are recycled. [citation needed]
Merocrine is the most common manner of secretion. The gland releases its product and no part of the gland is lost or damaged (compare holocrine and apocrine). The term eccrine is specifically used to designate merocrine secretions from sweat glands (eccrine sweat glands), [1] although the term merocrine is often used interchangeably. [2] [3]
The general secretion (Sec) involves secretion of unfolded proteins that first remain inside the cells. In Gram-negative bacteria, the secreted protein is sent to either the inner membrane or the periplasm. But in Gram-positive bacteria, the protein can stay in the cell or is mostly transported out of the bacteria using other secretion systems.
Unlike necrosis, apoptosis produces cell fragments called apoptotic bodies that phagocytes are able to engulf and remove before the contents of the cell can spill out onto surrounding cells and cause damage to them. [5] Because apoptosis cannot stop once it has begun, it is a highly regulated process.
Mucins (/ ˈ m juː s ɪ n /) are a family of high molecular weight, heavily glycosylated proteins (glycoconjugates) produced by epithelial tissues in most animals. [1] Mucins' key characteristic is their ability to form gels; therefore they are a key component in most gel-like secretions, serving functions from lubrication to cell signalling to forming chemical barriers. [1]